The present invention relates to a sensor device, for detecting a force that acts in a prescribed direction of force, having a magnetostrictive force sensor.
Various sensor devices are disclosed in the book “Sensors”, Vol. 5 (Magnetic Sensors), VCR Publishing Company, Weinheim (DE), 1989, pages 145 to 147, where the magnetoresistive effect is combined with other physical effects. Thus, for example, a force sensor is disclosed that takes advantage of the magnetoresistive effect and the Hall effect. For this purpose, there is produced in magnetostrictive components, via a constant current, a magnetic flux that under the effective force leads to a corresponding change in flux. This flux change is detected with a Hall element. Furthermore, the aforementioned book also describes a sensor device with which a magnetostrictive strip is connected with a piezoelectrical transducer. The magnetostrictive strip is magnetized by a DC field that is to be measured. The changing length of the strip connected therewith is converted via piezoelectrical transducer into an electrical measurement signal.
JP 11-251658 A discloses a magnitoresistance element according to which a tractive force is applied to an electrically conductive oxide film in such a way that the film is disposed, via a thin insulating layer, upon a substrate of magnetostrictive material, and the substrate is subjected to a magnetic field.
Pursuant to the not pre-published German Patent Application 102 14 946.1 of Apr. 4, 2002, a TMR sensor is proposed for the measurement of mechanical changes in length, in particular a compression and/or tension sensor that includes a sandwich system having two flat superimposed electrodes of magnetic material. These electrodes are separated by a tunnel barrier, in particular of oxidic material, whereby a current flow is effected between the electrodes through the tunnel barrier. One of the electrodes should be formed by an extension-sensitive, magnetostrictive detection layer in which the share of the anisotropy induced by a mechanical stress is greater than that of the intrinsic anisotropy, whereby during extension relative changes in resistance ΔR/R of the system of greater than 10% at room temperature develop.
It is an object of the present invention to provide a sensor device having a magnetostrictive force sensor or tension sensor, according to which a specially embodied TMR sensor is utilized that can be produced via known methods in the layer technology, especially thin film technology.